Lift max ram slots limit in libvhost-user

Historically, VMs with vhost-user devices could hot-add memory a maximum
of 8 times. Now that the VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS
protocol feature has been added, VMs with vhost-user backends which
support this new feature can support a configurable number of ram slots
up to the maximum supported by the target platform.

This change adds VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS support for
backends built with libvhost-user, and increases the number of supported
ram slots from 8 to 32.

Memory hot-add, hot-remove and postcopy migration were tested with
the vhost-user-bridge sample.

Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <1588533678-23450-11-git-send-email-raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libvhost-user/libvhost-user.h
index f8439713a8..844c37c648 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -28,7 +28,13 @@
 
 #define VIRTQUEUE_MAX_SIZE 1024
 
-#define VHOST_MEMORY_MAX_NREGIONS 8
+#define VHOST_MEMORY_BASELINE_NREGIONS 8
+
+/*
+ * Set a reasonable maximum number of ram slots, which will be supported by
+ * any architecture.
+ */
+#define VHOST_USER_MAX_RAM_SLOTS 32
 
 typedef enum VhostSetConfigType {
     VHOST_SET_CONFIG_TYPE_MASTER = 0,
@@ -55,6 +61,7 @@ enum VhostUserProtocolFeature {
     VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
     VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
     VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
+    VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
 
     VHOST_USER_PROTOCOL_F_MAX
 };
@@ -123,7 +130,7 @@ typedef struct VhostUserMemoryRegion {
 typedef struct VhostUserMemory {
     uint32_t nregions;
     uint32_t padding;
-    VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
+    VhostUserMemoryRegion regions[VHOST_MEMORY_BASELINE_NREGIONS];
 } VhostUserMemory;
 
 typedef struct VhostUserMemRegMsg {
@@ -190,7 +197,7 @@ typedef struct VhostUserMsg {
         VhostUserInflight inflight;
     } payload;
 
-    int fds[VHOST_MEMORY_MAX_NREGIONS];
+    int fds[VHOST_MEMORY_BASELINE_NREGIONS];
     int fd_num;
     uint8_t *data;
 } VU_PACKED VhostUserMsg;
@@ -368,7 +375,7 @@ typedef struct VuDevInflightInfo {
 struct VuDev {
     int sock;
     uint32_t nregions;
-    VuDevRegion regions[VHOST_MEMORY_MAX_NREGIONS];
+    VuDevRegion regions[VHOST_USER_MAX_RAM_SLOTS];
     VuVirtq *vq;
     VuDevInflightInfo inflight_info;
     int log_call_fd;